1. Technical Field
This invention relates to a brake system for a motorcycle which includes a bottom link type front wheel suspension, and rear disc brakes operated in synchronization with front disc brakes.
2. Background Art
Conventional synchronized brake systems are known in which a hydraulic rear disc brake operates in synchronization with a hydraulic front disc brake. An example of such a synchronized brake system is disclosed in Japanese Utility Model Laid-Open No. 3-120286, entitled xe2x80x9cSynchronized Brake System.xe2x80x9d The foregoing citation will be referred to as xe2x80x9cCitation (1)xe2x80x9d and the reference numerals of this document are used in the following description.
Referring to FIGS. 1 and 3 of Citation (1), the motorcycle includes the combination of a telescopic front wheel suspension and a synchronized brake system, in which the front wheel is rotatably attached to the bottom of a front fork 4. The brake disc 13 of the primary brake system 11 is attached to the front wheel, and the brake caliper 12 of the primary brake system 11 is attached to the bottom of the front fork 4 using an offset shaft 14. The secondary master cylinder 41 is coupled to the brake caliper 12 as an integral part.
When the brake lever 1 is operated, the brake caliper 12 brakes the disc brake 3. In this state, the cylinder body 42 of the secondary master cylinder 41 swings in response to a braking reaction force, and generates hydraulic pressure, which enables the rear brake system 31 to brake the rear wheel.
If a telescopic front wheel suspension is applied to a large motorcycle, spring/damper units having a large stroke should be used in order to ensure a large vertical stroke for a front wheel, which inevitably enlarges the spring/damper units. Conversely, when small stroke spring/damper units are utilized, a bottom link type suspension is relatively advantageous since the stroke of the spring/damper units can be made smaller using a link, with respect to the vertical stroke of the front wheel.
For example, Japanese Utility Model Laid-Open No. 6040396, entitled xe2x80x9cFront Wheel Suspension for Motorcyclexe2x80x9d, discloses a motorcycle including a bottom link type front wheel suspension. This citation will be referred to as xe2x80x9cCitation (2)xe2x80x9d. As shown in FIG. 1 of Citation (2), the upper parts of the front and rear arms 12, 13 are coupled to the lower part of the front fork 7, the rear part of the front wheel support 16 is coupled to the arms 12 and 13, the front wheel axle 20 is attached to the front part of the front wheel support 16, and the front wheel 11 is attached on the front wheel axle 20.
If the synchronized brake system disclosed in Citation (1) is incorporated into the motorcycle of Citation (2), it is impossible to attach the caliper to the front fork 7 of Citation (2). This is because the front wheel 1 swings vertically with respect to the front fork 7.
In order to overcome this problem, it is conceivable to attach the caliper and the secondary master cylinder to the front wheel support 16. However, since the bottom link type front wheel suspension is employed, the front wheel support 16 moves vertically with respect to the front fork 7, followed by the vertical movement of the caliper and the secondary master cylinder. As a result, the secondary master cylinder is caused to operate in addition to the braking operation. This additional operation of the secondary master cylinder is not preferable. Therefore, it is impossible to easily incorporate the technique of Citation (1) into Citation (2).
For the purpose of overcoming the foregoing shortcomings, a special transmitting mechanism may be provided, in which a secondary master cylinder is attached to the front fork 7, and a caliper is attached to the front wheel supports 16, so that braking reaction force is transmitted to the secondary master cylinder via the caliper. However, this arrangement complicates the bottom link type front wheel suspension and the synchronized brake system, and leaves much room for improvement.
This invention in part is therefore intended to provide a technique which assures appropriate and smooth synchronized operation of a simple synchronized brake system in a motorcycle having a bottom link type front wheel suspension.
The present invention accomplishes the foregoing object and other advantages not contemplated by conventional art.
An embodiment of the invention provides a brake system for a motorcycle including a bottom link type front wheel suspension, hydraulic front disc brakes, and a hydraulic rear disc brake. The brake system includes brackets which are attached to a front wheel axle and orthogonal thereto. Calipers for the hydraulic front disc brakes are attached to the brackets, and tips of the brackets are coupled to a front fork via torque transmitting links. A master cylinder is attached on the middle of one of the torque transmitting links, and generates hydraulic braking pressure for operating the hydraulic front disc brakes. The master cylinder is activated in response to compressive force applied to the torque transmitting links, and brakes a rear wheel.
When the hydraulic front disc brakes brake the front wheel, the braking reaction force of the front wheel acts as compressive force (axial tension) on the torque transmitting links from the calipers, and acts on the master cylinder provided on one of the torque transmitting links. Therefore, the master cylinder generates braking hydraulic pressure, which acts on the calipers of the hydraulic rear disc brake, thereby braking the rear wheel. No special transmitting mechanism is required in order to transmit the braking reaction force to the master cylinder from the calipers. Further, it is not necessary to extensively modify the bottom link type front wheel suspension.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.